The present invention relates to an improved door, particularly a coke oven door, of the self-locking type. More particularly, the present invention is directed to such an improved door wherein the weight of the door itself causes locking of the door against a door frame of the type having extending outwardly therefrom vertically spaced pairs of support hooks for supporting the door.
A door of this type is disclosed in German Patent No. 908,608, wherein a door element, adapted to be sealed against a door frame and close a door opening in the door frame, carries a pair of vertically spaced horizontally extending locking bars. Each locking bar has opposite round ends adapted to rest on and be held by a respective pair of support hooks of the door frame. When the door is placed in position with the locking bars positioned on the hooks, the weight of the door causes the locking bars to be pivoted about horizontal axes away from the door element. Thus, the door is pressed against the sealing frame. This known device also includes an arrangement whereby the locking bars are carried by respective locking support members which are guided for vertical movement along the door element by means of angular elements or brackets. Connecting rods attached to the locking support members are hinged on a two-arm lever which is pivoted to the door element to form an equalizer linkage assembly for equalizing contact position of the locking bars with the respective hooks, by allowing relative vertical movement of the locking support members toward or away from each other.
However, this known type of door has certain inherent disadvantages.
Specifically, the locking support members tend to jam in their respective angular brackets due to the heavy weight of the door element and the thus inherent high frictional forces involved. Accordingly, the equalizer linkage mechanism is not always effective to equalize seating or contact of the locking bars with the respective hooks. This causes uneven sealing contact pressure of the door against the door frame.
A further problem involved in the known door disclosed in German Pat. No. 908,608, is that upon relative movement of the rounded ends of the locking bars with respect to the hooks, considerable friction resistance is encountered. This is an additional friction force tending to retard movement of the elements toward a smooth and even door locking position. Furthermore, this frictional resistance requires a greater lifting force to be applied to the door to unlock the door.
An even further disadvantage of the door disclosed in German Pat. No. 908,608 is due to the fact that the equalizer linkage assembly is provided with a turnbuckle and a worm gear to provide for necessary adjustment due to differing lengths of connecting rods connecting the locking support members and the two-arm lever and due to differing vertical spaced positions of the pairs of hooks of the door frame.